Rare & Historic Transit of Venus Across Sun Occurs Today

Below:

Next story in Space

Skywatchers have the opportunity to witness history today (June
5), as the planet Venus rambles across the face of the sun in a
rare event that will not be visible again for 105 years.

Astronomers call this orbital encounter the " transit
of Venus," when the planet passes between Earth and the sun,
appearing as a tiny black blemish as it travels across the solar
disk.

Transits of Venus are some of the rarest skywatching sights
because they happen so infrequently. Transits occur in pairs
eight years apart, once every 100 years or so. Today's transit is
paired with a previous one that occurred on June 8, 2004. Before
that, the last pair of Venus transits
wowed astronomers and explorers in 1881 and 1889.

Anyone who misses today's event, however, will be out of luck,
because the next two transits of Venus will not occur again until
the year 2117 and 2125.

Luckily, much of the world will be well-placed to view at least
part of the Venus transit, weather permitting. Observers in North
America, Europe, Asia and eastern Africa should be treated to the
spectacular and historic views, provided local weather
cooperates. [ Venus
Transit of 2004: 51 Amazing Photos ]

How to watch

The transit will begin around 6 p.m. EDT (3 p.m. PDT; 2200 GMT)
this evening, and will last approximately seven hours. Since the
transit of Venus is happening across the International Date Line,
it will occur on Wednesday (June 6) in Asia, Australia, Africa
and Europe.

In North America, the
best time to see the transit will be in the hours before
sunset today. People located in the mid-Pacific region, where the
sun will be high overhead during the transit, will be able to
witness the majority of the event.

In Europe, Africa and Australia, Venus will be crossing the face
of the sun as it rises in the morning on June 6. Skywatchers in
Asia and across the Pacific Ocean should be able to view the
transit any time on Wednesday, weather permitting.

WARNING: It is very important to exercise
caution and
protect your eyes during the transit of Venus. It is
very dangerous to stare directly at the sun. Special
eclipse glasses or solar filters for telescopes are needed to
avoid permanently damaging your eyes.

Have fun but be careful!

To safely view the transit, special solar filters should be
fitted over binoculars or telescopes, and eclipse glasses or No.
14 welder's glasses should be used as protective eyewear.
[ Video:
How to Make a Solar Eclipse Viewer ]

The safest and simplest technique is to view the transit
indirectly using a solar projection. Skywatchers can use
telescopes or one side of a pair of binoculars to project a
magnified image of the sun's disk onto a shaded white piece of
cardboard. This projected image is
safe to look at and photograph, but it's important to
remember to cover the telescope's finder scope and the other half
of the binoculars to avoid accidentally looking through them.

It will take about 18 minutes for Venus to fully trek onto the
face of the sun, proceeding on a diagonal track across our
nearest star.

Astronomers refer to the different phases of the transit of Venus
as "contacts." When the planet first touches the outer edge of
the sun, this is known as first contact. Second contact occurs
when Venus appears to be completely on the sun. Third contact
refers to when Venus touches the sun's inner edge, and fourth
contact follows when the planet is totally separate from the sun.

For skywatchers in the eastern parts of the U.S. and Canada,
first contact should occur around 6:03 p.m. EDT (3:03 p.m. PDT;
2203 GMT).

NASA astronaut Don Pettit, who is currently partway through a
months-long stint aboard the International Space Station, is
planning to become the first person to photograph the transit of
Venus from space. Pettit will be snapping pictures of the
celestial event from the space station's seven-windowed Cupola
observation room.

NASA's Solar Dynamics Observatory will also be used to stare at
the transit from space. The sun-watching satellite will use its
observations to calibrate its instruments, as well as help
researchers gain more insight into Venus' hellishly hot
atmosphere.

The European Space Agency's Venus Express and Proba-2 spacecraft
will also be monitoring Venus and the sun during the transit. The
Hubble Space Telescope plans to use the moon as a giant mirror to
measure the light that passes through the atmosphere of Venus and
is reflected onto the moon during the transit.For those who are
unable to witness the transit of Venus in person, NASA and
several observatories will be
broadcasting live footage online from telescopes around the
world. Members of the public can tune into the webcasts to see
real-time views of the transit, coupled with commentary from
astronomers and transit experts.

SPACE.com will has collected several
Venus transit webcasts as part of our complete
coverage, in addition to reporters scattered at various transit
events in different cities.

Assistant managing editor Clara Moskowitz will be attending a
special event hosted by the Amateur Astronomers Association of
New York at the High Line park on Manhattan's West Side. Staff
writer Denise Chow will be stationed at an event at the American
Museum of Natural History, where astronomer Steve Beyer will
provide commentary during live views of the transit from the
Mauna Kea Observatory in Hawaii.

Senior writer Mike Wall will be covering the transit of Venus
from NASA's Ames Research Center in Moffett Field, Calif.

Editor's note: If you snap photos of the 2012
transit of Venus across the sun and would like to share them with
SPACE.com, send images and comments to managing editor Tariq
Malik at: tmalik@space.com.

Follow SPACE.com for the latest in space science and
exploration news on Twitter@Spacedotcomand onFacebook.